3P680 in Photosystem II with Singly Reduced QA

Schlodder, E.; Hillmann, B.; Brettel, Klaus; Mallwitz, F.

doi:10.1007/978-94-011-3953-3_254

Cited by 4 publications

(10 citation statements)

References 7 publications

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“…The P680 triplet state has been monitored in the presence of singly reduced Q A by transient absorbance spectroscopy Schlodder et al 1998) and time-resolved electron paramagnetic resonance (EPR) (Feikema et al 2005). Under these conditions, the triplet decay is two or three orders of magnitude faster À -P680Q A Þ absorbance difference spectra of PSII core complexes from the wild-type (WT) and the (a) D1-His198Gln mutant and from the wild-type (WT) and the (b) D1-Thr179His mutant measured at 80 K. The spectra were normalized to K1 at the bleaching minimum to allow better comparison.…”

Section: Resultsmentioning

confidence: 99%

“…When electron transfer to the first PSII quinone acceptor, Q A , is blocked, the primary radical pair, P680 C Pheo K , decays with high yield at low temperature, after singlet-triplet mixing in the radical pair, by recombination to the lowest excited triplet state of P680, 3 P680 (Schlodder et al 1998). The P680 triplet state has been monitored in the presence of singly reduced Q A by transient absorbance spectroscopy (van Mieghem et al 1995;Schlodder et al 1998) and time-resolved electron paramagnetic resonance (EPR) (Feikema et al 2005). Under these conditions, the triplet decay is two or three orders of magnitude faster…”

Section: Resultsmentioning

confidence: 99%

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Site-directed mutations at D1-His198 and D1-Thr179 of photosystem II in Synechocystis sp. PCC 6803: deciphering the spectral properties of the PSII reaction centre

Schlodder

Coleman²,

Nixon

et al. 2007

Phil. Trans. R. Soc. B

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Site-directed mutations were constructed in photosystem II of Synechocystis sp. PCC6803 in which the axial ligand, D1-His198, of special pair chlorophyll P D1 was replaced with Gln and where D1-Thr179, which overlies monomeric chlorophyll Chl D1 , was replaced with His. The D1-His198Gln mutation produces a 3 nm displacement to the blue of the bleaching minimum in the Soret and in the Qy region of the P-PQ A Þ absorbance difference spectrum. To a first approximation, the bleaching can be assigned to the low-energy exciton transition of the special pair chlorophylls P D1 /P D2 . The D1-Thr179His mutation produces a 2 nm displacement to the red of the bleaching minimum in the Qy region of the ( 3 P-1 P) absorbance difference spectrum. Analysis of the flashinduced P-PQ A Þ and ( 3 P-1 P) absorbance difference spectra of both mutants compared with wild-type at 80 K indicate that the cation of the oxidized donor P C is predominantly localized on the chlorophyll P D1 of the special pair and that the reaction centre triplet state, produced upon charge recombination from 3 [P C Pheo K ], when the primary quinone electron acceptor Q A is doubly reduced, is primarily localized on Chl D1 .

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Site-directed mutations at D1-His198 and D1-Thr179 of photosystem II in Synechocystis sp. PCC 6803: deciphering the spectral properties of the PSII reaction centre

Schlodder

Coleman²,

Nixon

et al. 2007

Phil. Trans. R. Soc. B

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“…When electron transfer to the first PS II quinone acceptor (Q A ) is blocked, the RC triplet state 3 P is formed with high yield at low temperature by charge recombination of P680 + Pheo D1 − after singlet–triplet mixing in the radical pair state . In the presence of singly reduced Q A , the triplet state decay is 2 or 3 orders of magnitude faster than when Q A is doubly reduced ,, . Double reduction of Q A can be achieved by illumination of PS II core complexes in the presence of dithonite .…”

Section: Discussionmentioning

confidence: 99%

“…When electron transfer to the first PS II quinone acceptor (Q A ) is blocked, the RC triplet state 3 P is formed with high yield at low temperature by charge recombination of P680 + Pheo D1after singlet-triplet mixing in the radical pair state (30). In the presence of singly reduced Q A , the triplet state decay is 2 or 3 orders of magnitude faster than when Q A is doubly reduced (30,61,62). Double reduction of Q A can be achieved by illumination of PS II For the D1-Thr179His mutant, the wavelength corresponding to the site energy of Chl D1 was shifted by 2.5 nm to the red relative to 679.5 nm in WT.…”

Section: Explanation Of the Mutation-induced Shift Of The Transitionmentioning

confidence: 99%

“…When electron transfer beyond Pheo is blocked by prereduction or by removal of the primary quinone acceptor Q A , then the RC triplet state 3 P is formed, in high yield at low temperatures, by charge recombination of P680 + Pheo D1 − following singlet–triplet mixing in the radical pair state . EPR studies with oriented PS II samples have shown that the plane of the Chl, which carries the triplet state, is oriented like that of the accessory chlorophylls , that is, the triplet state is localized on one of the accessory chlorophylls, most probably on Chl D1 ,, .…”

mentioning

confidence: 99%

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Site-directed Mutations at D1-Thr179 of Photosystem II in Synechocystis sp. PCC 6803 Modify the Spectroscopic Properties of the Accessory Chlorophyll in the D1-branch of the Reaction Center

et al. 2008

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D1-Thr179, which overlies the reaction center chlorophyll Chl D1 of Photosystem II was replaced with His and Glu through site-directed mutation in Synechocystis sp. PCC 6803. Spectroscopic characterization of the mutants indicates that, compared to wild type, the main bleaching in the triplet-minus-singlet absorbance difference spectrum and the electrochromic band shift in the (P680 (+)Q A (-)-P680Q A) absorbance difference spectrum are displaced to the red by approximately 2 nm in the D1-Thr179His mutant and to the blue by approximately 1 nm in the D1-Thr179Glu mutant. These difference spectra are compared with the absorbance difference spectra, measured on the same states in the D1-His198Gln mutant in which the axial ligand D1-His198 of the special pair chlorophyll, P D1, was replaced by glutamine. Together, these results give direct evidence that (a) the reaction center triplet state, produced upon charge recombination from (3)[P (+)Pheo (-)], is primarily localized on Chl D1; (b) the cation of the oxidized donor P (+) is predominantly localized on chlorophyll P D1 of the special pair; and (c) the Q Y band of the accessory chlorophyll Chl D1 is electrochromically shifted in response to charges on P (+) and Q A (-). Light-induced absorbance difference spectra (between 650 and 710 nm), associated with the oxidation of secondary donors and the reduction of Q A, exhibit a bleaching attributed to the oxidation of a Chl Z and strong electrochromic band shifts. On the basis of mutation-induced spectroscopic changes and of structure-based calculations, we conclude that the experimental spectra are best explained by a blue-shift of the Q Y band of the accessory chlorophyll Chl D1, arising from charges on Car D2 (+) and Chl ZD2 (+) and on reduced Q A.

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Triplet Delocalization over the Reaction Center Chlorophylls in Photosystem II

et al. 2023

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The triplet state of chlorophyll formed by charge recombination in photosystem II (PSII) is a precursor of harmful singlet oxygen. Although main localization of the triplet state on the monomeric chlorophyll, ChlD1, at cryogenic temperatures has been suggested, how the triplet state is delocalized on other chlorophylls remains unclear. Here, we investigated the distribution of the triplet state of chlorophyll in PSII using light-induced Fourier transform infrared (FTIR) difference spectroscopy. Measurements of triplet-minus-singlet FTIR difference spectra with PSII core complexes from cyanobacterial mutants, D1-V157H, D2-V156H, D2-H197A, and D1-H198A, in which the interactions of the 131-keto CO groups of the reaction center chlorophylls, PD1, PD2, ChlD1, and ChlD2, respectively, were perturbed, identified the 131-keto CO bands of the individual chlorophylls and showed that the triplet state is delocalized over all of these chlorophylls. It is suggested that the triplet delocalization plays important roles in the photoprotection and photodamage mechanisms in PSII.

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3P680 in Photosystem II with Singly Reduced QA

Cited by 4 publications

References 7 publications

Site-directed mutations at D1-His198 and D1-Thr179 of photosystem II in Synechocystis sp. PCC 6803: deciphering the spectral properties of the PSII reaction centre

Site-directed mutations at D1-His198 and D1-Thr179 of photosystem II in Synechocystis sp. PCC 6803: deciphering the spectral properties of the PSII reaction centre

Site-directed Mutations at D1-Thr179 of Photosystem II in Synechocystis sp. PCC 6803 Modify the Spectroscopic Properties of the Accessory Chlorophyll in the D1-branch of the Reaction Center

Triplet Delocalization over the Reaction Center Chlorophylls in Photosystem II

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